Optical properties and dielectric relaxation of polypyrrole and poly (3-hexylthiophene)

Abstract In the present work, polypyrrole (PPy) and poly (3-hexylthiophene) (P3HT) are prepared via oxidation polymerization, and their optical and dielectric properties in comparison with their originating monomers are investigated. The chemical structure of both polymers is confirmed by FTIR spectroscopy. Investigation of the optical properties of the prepared polymers showed that the band gap of PPY is 1.25 eV, whereas that of P3HT is 1.79 eV. In addition, P3HT showed a refractive index of high values in the visible region compared to PPy. Dielectric relaxation of both monomers and polymers was studied in the frequency range of 10 –1 ≤ ν /Hz <10 7 for comparison. Furthermore, temperature dependencies of their electrical properties are investigated. The DC conductivity values of PPy and P3HT are found to be 2× 10 –7 S cm −1 and 2× 10 –4 S cm −1 , at T = 313 K, respectively, which is the ranges of semiconductors and conductors reflecting the remarkable enhancement of conductivity according to the polymerization process. The temperature dependence of the DC conductivity for the monomers and polymers follows the Vogel−Fulcher−Tammann (VFT) equation. The parameters of the frequency-dependent provide basic information for adjustment of the structural properties of the conjugated polymers and finding the theoretical limits controlling the charge transport.